Ignition apparatus



2 Sheets-Sheet l F. mass IGNITIONAPPARATUS Filed Dec. 14, 1938 f 0677 01".- Wed March 10, 1942.

F. MIESS IGNITION APPARATUS 2 Sheets-Sheet 2 Filed Dec. 14, 1938 w EE l QMBRMB O O m E a I 335 w F H w 4; J K Id w w/ EM 1K4] 3o Patented Mar. 10, 1942 UNITED STATES PATENT OFFICE,

2,275,861 rem'rron APPARATUS Fred Miess, Gary, Ind. Application December 14,1938,Serial No. 245,765

6 Claims.

ther feature is that the apparatus is very simple and rugged; yet another feature of the invention is that in certain embodiments means may be provided for actuating valve means or the like in accordance with the presence or absence of such intermittent impulses; other features and advantages of this invention will be apparent from the following specification and the drawings, in which:

Figure 1 is a schematic diagram of my inven tion in simple form; Figure 2 is a representation of the current flow; and Figure 3 is an illustration, partly schematic, of an industrial embodiment of my invention.

Ignition apparatus now in general use-is of two main types. One is the make and break type found in automobile or other internal combustion engine ignition systems, where a primary circuit of a step-up transformer is opened and closed to effect periodic generation of energy in the secondary of the transformer. The other is the type more generally found in industrial applications, and consists of a step-up transformer directly connected to an alternating current line, so that there is a continuous arcing across the ignition points.

This latter type makes a very simple, rugged and reliable ignition system especially adapted to the Supplying simultaneously of ignition impulses to a large number of gaps or pairs of points. This type, for example, is generally found on industrial furnaces having large numbers of fuel jets or burners as, for example, annealing furnaces in the steel industry. For reasons concerned with safety, such ignition apparatus is generally run continuously while fluid fuel is being supplied to the furnace; and this results in one of the principal objectionable features of such a system, a large energy consumption. An industrial annealing furnace with a large number of fuel jets will frequently draw three kilowatthours per hour.

My invention is equally rugged and reliable, is adapted to use the same transformers and points when used as ignition for an annealing furnace,

for example, and will give equivalent ignition.

with only about five per cent,of the power consumption. This invention comprises the use of a condenser to supply periodic strong impulses,

r the other.

the condenser being charged, between such impulses, from some primary source of current.

A simple embodiment of my invention is illustrated in Figure 1. A condenser III has oneplate thereof connected to the movable element ll of a single-pole double-throw switch or relay which is adapted to connect it to either of two circuits; and the other plate is connected, in common, to the returns of each of such circuits. The switch is here illustrated as-having two con"- tact points I2 and I3, and as being provided with means for periodically connecting the movable element H to one of said points and then to This is here shown as a cam ll mounted on a continuously rotating shaft 15 driven by any conventional means.

One of the circuits, which may be termed the charging circuit, includes a source of power such as the battery 16, a current limiting means such as the resistor i1, and the contact l2. When the movable switch element II is in the position shown in solid lines a charging circuit for the condenser is thus completed, and the condenser is charged to a desired voltage.

The other or discharge circuit includes the contact point 13 and the primary of step-up transformer i8. The secondary of this transformer is connected to any desired electrical apparatus, as a pair of separated ignition points l9 and 20. When the movable switch element II has been placed in the position shown in dotted lines by the rotation of the cam the discharge circuit is completed and the energy which was stored in the condenser is delivered in a brief strong electrical impulse to the ignition points.

Referring more particularly to Figure 2, the various current flows are illustrated. When the movable switch element ll makes engagement with the switch contact [2, current is supplied from the battery I6 to charge the condenser 10. This current substantially immediately jumps to a value fixed by the resistor i1, here shown as about 27 amperes; and thereafter the current tapers down in substantially the manner illustrated in the first flve-hundredths of a second on the curve. While the condenser is not theeretically fully charged, it is fully charged for all practical purposes; and the switch is so arranged that the charging circuit is disconnected at this time by separation of-the switch element tically no current which is the chief factor in enabling very large currents to be handled without injury to switches, thus permitting a number of industrial furnaces to be supplied from one ignition unit. In the embodiment here being described it is assumed that at the end of onetenth second after the switch element H engages the contact point l2 it engages contact point II! in the discharge circuit. The condenser will then discharge through the transformer to provide a strong electrical impulse of brief duration, as indicated in Figure 2. While the maximum charging current was relatively low the condenser and transformer may be so arranged that the brief discharge current is of high amperage. In the assumed embodiment here being described this is shown as reaching a peak value between two and three hundred amperes. This, of course, effects a very hot spark of good igniting characteristics across the points l9 and 20.

Inasmuch as the shaft continuously rotates at a regular rate, at about one-tenth of a second after the discharge the condenser will again start to charge, and the cycle would be repeated.

A simplified commercial embodiment of my invention is illustrated in Figure 3. Here the wires 22 and 23 are connected to a source of direct current, as for example about 375 volts delivered by a motor generator set. This current acts through a resistor 24 and switches, which will be hereinafter more fully described, to periodically charge the condenser 25. Although here diagrammatically shown as a single pair of plates, in practice such condenser would usually comprise a number oi. electrolytic or paper condensers connected in parallel to pro vide the electrical effect of a single condenser of considerable capacity. The switch means periodically discharges the condenser through the wires 26 and 21. These wires are connected to a number of parallel ignition circuits. For example, wires 28 and 29 lead to an annealing furnace 30, and have connected thereto in series arrangement the primaries of transformers 3| and 32. The secondaries of these transformers are connected to separated ignition points, as 33 and, in igniting relationship to a stream of fluid fuel, as gas being delivered by the jet 35. Another pair of branch leads, as 36 and 31', may

lead to the primaries of a plurality of ignition transformers (here shown, as a modification, in parallel arrangement) in another annealing furnace 38.

It has been found preferable to employ rockable mercury switches to effect the connecting and disconnecting, rather than a movable mechanical switch element of the type illustrated diagrammatically in Figure 1. To secure effective ignition, however, there must be several impulses per second, preferably about ten a second, delivered to the ignition points. This is so rapid that a single mercury switch would not be efiective, since if an attempt were made to rock it at such a speed the mercury would splash and the action would be erratic. In order to solve this switch difliculty, therefore, each of the connecting and disconnecting means comprises a plurality of parallel circuits, each circuit including two mercury switches in series therein.

For example, I can employ a plurality of twoa element mercury switches, here identified as 39 to 46. The switches indicated by odd reference numerals are the charging switches, 39 and 4| being in series in one charging circuit and 43 and 45 in a second parallel charging circuit.

Switches 40 and 42 are in series in one discharging circuit adapted to connect the condenser 25 to the ignition supply lines 26 and 21; and switches 44 and 46 are in a second parallel condenser discharging circuit.

All of the mercury switches are of similar construction, and are of the conventional twoelement type wherein a pair of separated elements are sealed in a small glass tube having a small quantity of mercury therein. Referring to one of the switches, as 39, it will be seen that it is mounted upon an arm 41 adapted to be rocked about the pivot point 48. Rocking of this arm is effected by cam 49 mounted on continuously rotating shaft 50 driven by any conventional means. The other switches are similarly mounted and driven, switch 4|, for example, being driven by the cam 5|.

The particular arrangement shown is employed to enable relatively small movement of the switches to effect the desired making and breaking of the various circuits with great rapidity. The switches in series in each particular circuit are arranged to b rocked out of step with each other, with a predetermined time relationship therebetween. Considering first switches 38 and 4|, it will be seen that as the shaft 50 rotates cam 5| first closes switch 4| while switch 39 is still open; and the latter switch 39 was closed to complete a charging circuit to the condenser 25. The cam 5| has continued to rotate, however, and therefore very shortly after switch is closed to complete the charging circuit switch 4| opens to break it. It will be seen that the time relationship between the cams can thus be arranged to hold this closed circuit interval to a very brief one, a matter of hundredths of a second when desired. It will. be noted that the slight further rotation of the shaft 50 which breaks switch 4| closes switch and that switch 42 is already in closed position. Thus in a very brief interval after the charging circuit has been disconnected from the condenser 25 the condenser is connected, through the switches 40 and 42, to the ignition lines 25 and 21 to deliver its desired ignition impulse thereto. Switch 42, however, is already rocking in the opening direction; and again, very shortly after switch 4|! has completed connection of one of the discharge circuits, switch 42 opens it. The cycle is then repeated in a pair of parallel charging and discharging circuits; that is, shortly after switch 42 breaks or opens, switch 43 closes to charge the condenser through itself and switch and as soon as 45 opens the condenser is discharged through a circuit completed by switches 44 and 46. Such a switching arrangement enables any desired number of ignition impulses to be de livered per second, with a relatively slow rocking of the mercury switches which is a factor of their number. That is, in the embodiment illustrated two ignition impulses per second would be delivered with only one rocking cycle per second of the mercury switches; with ten sets of parallel circuits on both the charge and discharge side, rather than two as shown, ten impulses per second can be delivered with only one rocking cycle per second of each switch.

In order to prevent any danger of an explosion as a result of flame failure, each furnace is here shown as provided with electrical actuating means here identified as 53 and 54, which means are adapted to actuate any conventional type of electric valve to shut off the stream of fluid fuel being supplied to the furnace. Such a failure of ignition impulses might be occasioned by opening the switches at any particular furnace, or by complete failure of the entire system for some reason, as burning out of the motor generator. The actuating means here shown as solenoids 53 and 54 are adapted to be supplied with current from a separate source of any type connected to the lines 55 and 56. One of these lines, here shown as 55, is connected to one side of each of the solenoids 53 and 54, as by the branch leads 5'! and 58. The other lead, as 56, is connected through a relay 59 to the center point of an impedance 60 having the ends thereof connected to the ignition supply lines 26 and 21. The other end of each of the solenoids 53 and 54 is connected, through balanced or centering means, to the-branch ignition circuits at each furnace. In furnace 38 this connection is shown as made to the center point of a separate impedance element 6| having its ends connected to the branch ignition supply lines 36 and 31 furnishing ignition impulses to that particular furnace. The arrangement shown in furnace 30 is a modified form achieving the same result, by using the primaries of the transformers 3| and 32, rather than a separate impedance, to complete the circuit from the solenoid 54.

In order to insure cessation of .fuel flow if the whole ignition circuit becomes inoperative, the

relay 59 is arranged to open. In the particular form here shown a rectifying tube 63 is adapted to transform the oscillating ignition impulses into unidirectional charging impulses to condenser" 65. Condenser 65 supplies holding current for relay 59 through its winding 64 to keep the relay closed as long as charging impulses to condenser 65 continue at regular intervals. Current from condenser 65 through winding 64 bridges the period when there is no current flow through the rectifying tube.

While I have described and claimed certain embodiments of my invention it is to be understood that it is capable of many modifications. Changes,, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims, in which it is my intention to claim all novelty inherent in my invention as broadly as permissible in view of the prior art.

I claim:

1. Apparatus of the character described for pcriodically supplying a strong electrical impulse of short duration from a source of electrical energy, including: a condenser; a source of current adapted to charge said condenser; means for limiting the charging flow of current; and means for periodically connecting said condenser to the circuit to which said strong impulse is to be delivered, the second named means comprising a pair of mercury switches in series rocked, with a predetermined time relationship therebetween, by a continuously rotating shaft.

2-. Apparatus of the character described for periodically supplying a strong electrical impulse of short duration from a source of electrical energy, including: a condenser; a source of current adapted to charge said condenser means for limiting the charging flow of current; and means for periodically connecting said condenser to the circuit to which said strong impulse is to be delivered, said connecting means comprising a plurality of parallel circuits, each circuit including in series therein a switch. a

3. Apparatus of the character described for periodically supplying a strong electrical impulse of short duration from a source of electrical energy, including: a condenser; a source of current adapted to charge said condenser; means for limiting the charging flow of current; and

, means for periodically disconnecting said condenser from said source and connecting it to the circuit to which said strong impulse is to be delivered, said connecting and disconnecting means each comprising a plurality of parallel circuits, each circuit including in series therein a pair of switches, all of said switches being operated, with a predetermined time relationship therebetween, by a continuously rotating shaft.

4. Apparatus for simultaneously energizing a relatively large number of spark gaps with sparking current, including a circuit interconnecting all said gaps for simultaneously energizing the same, a condenser, a resistance, a source of direct electric current, means for alternately connecting and disconnecting said source in series with said condenser and said resistance, and means for charging said circuit from said condenser when said source is disconnected therefrom, the first named means including switches working at a 'speed proportioned respecting the electrical characteristics of said resistance to permit the initial current flowing through said switches when said source is connected to said condenser and said resistance, to practically terminate prior to said switches disconnecting said source from said condenser and said resistance.

5. Apparatus for simultaneously energizing a relatively large number of spark gaps with sparking current, including a circuit interconnecting all said gaps for simultaneously energizing the same, a condenser, a resistance, a source of direct electric current, means for alternately connecting and disconnecting said source in series with said condenser and said resistance, and means for charging said circuit from said condenser when said source is disconnected therefrom, the first named means including switches working at a speed proportioned respecting the electrical characteristics of said resistance to permit the initial current flowing through said switches when said source is connected to said condenser and said resistance, to practically terminate prior to said switches disconnecting said source from said condenser and said resistance, said switches being mercury switches provided with means for rocking them sufficiently slowly to prevent splashing of their mercury.

6. Apparatus for simultaneously energizing a relatively large number of spark gaps with sparking current, including a circuit interconnecting all said gaps for simultaneously energizing the same, a condenser, a resistance, a source of direct electric current, means for alternately connecting and disconnecting said source in series with said condenser and said resistance, and means for charging said circuit from said condenser when said source is disconnected therefrom, the first named means including switches working at a speed proportioned respecting the electrical,

characteristics of said resistance to permit the initial current flowing through said switches when said source is connected to said condenser and said resistance, to practically terminate prior to said switches disconnecting said source from said condenser and said resistance, said resistance having an electrical value limiting the flow of said initial current to a value safely within the capacity of said switches.

FRED MIESS. 

